Raw material refers to the stone from which debitage, tools etc. are produced. A number of raw materials were used in pre-history, the most common feature of these materials is that they have the property of conchoidal fracture thus enabling the knapper to control the core and produce predictable outcomes of the knapping procedure.
Raw materials cover the minerals and rocks that were utilized to produce tools during the Stone Age. These raw materials have certain properties which makes it possible for a toolmaker to control and predict the production of tools by using intentionally chosen methods and techniques. This overview is not complete, but gives a good impression of preferred raw materials in the norwegian Stone Age. The overview seeks to explain why these raw materials were selected for tool production.
Most lithic raw material is procured as nodules (nodules have rounded edges but can be in various shapes as opposed to a cobble which is rounded and roughly spherical). Flint is most often found in this form but there is also tabular flint that is procured from vertical or horizontal seams. Other lithic raw materials may be procured from eroded out material. Raw material such as slate will come in parallel-sided slabs.
Geology is the science of the Earth and especially the composition of the earth’s crust and its development through time. Almost every natural raw material is found in the geological construction of the crust (Bjørlykke 2000:9).
Geology in archaeology
Minerals and rocks are the most stable and resistant materials of the earth’s surface. This is why Stone Age tools produced in these materials will outlast tools of organic materials. Thus, knowledge of geology is important to explore the largest source of information of the early prehistory. During the Stone Age a number of different minerals and rocks were utilized. For the prehistoric toolmaker the procurement of applicable raw material was the first, and most important, step of the tool production.
The availability of high quality raw materials vary, and is further limited by the geological circumstances of a given area. In many cases, the localization of a site and the movement across the landscape (mobility) can be more or less determined by the raw material sources. As archaeologists, it is important to know where certain types of raw materials can be found and which properties they inhabit. As such it is important to know how minerals and rocks are defined and separated into distinct groups after their geological origin.
Raw material types
A rock consists of two or more minerals (Dons 1996:7). Rocks are divided into three main categories based on origin. These categories are described in their separate pages
A mineral is a chemical element or a chemical compound formed by geological processes (Dons 1996:7). There exists over 4000 minerals, but only between 20-25 of these are common enough to form rocks. A few examples of well known minerals are quartz, feldspar, orthoclase, fluorite, muscovite and olivine. Every mineral has a specific chemistry and structure which gives it distinctive physical properties like color, hardness and fracture. It is the chemical compound which is the key to understand why some minerals were exploited in prehistory. Quartz (Sio2) is the most constant of all minerals, and fine grained variants of this mineral (silicates) were often utilized to make tools.
Silicate raw materials
Igneous raw materials
Sedimentary raw materials
Metamorphic raw materials
Modern raw materials
Other raw materials
Main article: Natural alteration.
Raw material, and the products of a given raw material, can be altered by both natural and human processes before, during and after production. These alterations can change the quality and appearance of a raw material which make it more difficult to interpret. Below a number of terms and processes are described to make it easier to explain what we observe.
Lithic material can altered by natural processes so that they sometimes resemble tools. Such lithics are known as eoliths. Also some lithic material can appear to be polished by agencies such as wind and sand, often referred to as desert polish. Also debitage can be altered by natural processes such as heat, frost